Television apparatus



E. C, MEYER TELEVISION APPARATUS BEHQE Filed Oct. 22, 1934 l i i lPatented Feb. i4, 'w39 TELEVESPN FPARAEUS Eugene Carl Meyer,lifiiiwaukee, Wis., assigner to r/ i/Verner, lliiiwanhee, Wis.

Appiication @atelier 22, i934, Serial No. 7%,393

3 Claims.

This invention relates to improvements in television apparatus.

It is the primary object of the invention to provide novel and improvedscanning means and novel and improved light controlling means. Thescanning means is used both in the pick-up device and in the reproducingdevice. The improvements contemplated by this invention are such asgreatly to simplify and reduce the expense of television apparatus,whether such apparatus is used in conjunction with line communication orradio.

The illustration of the invention in the drav ing is purelydiagrammatic.

Figures l and 2 are plan and side views, respectively, showing thereproduction device used at the receiving end.

Figure 3 is a view of the reproduction chamber and shutter chamber insection, indicating -diagramniatically its operating connections.

Figure 4 is a View of the photoelectric chamber illustratingdiagrammatioally its connections.

Figure 5 is a detail view showing, in perspective, the mechanism whichmodulates the intensity of the light in the reproducingsystem, the holein the shutter being disproportionately enlarged.

Like parts are identified by the same reference characters throughoutthe several views.

It being broadly immaterial how the television signals are transmitted,I have chosen to illustrate the invention from the standpoint of radiotransmission. A conventional radio transmitting apparatus is shown atpreferably having a ground connection at 5 and an antenna ccnnecm tionat 1'?. The carrier wave produced therein in the usual mann-er ismodulated by the current impulses from a photoclectric cell l, which isalmost completely enclosed in a cabinet 8 and exposed only to such lightas enters the cabinet through the aligned oriiices 9 and it, therelative size of which is necessarily greatly exaggerated in thedrawing. rihe area of the light beam admitted to the photoelectrio celll will be no greater than the theoretical area known optically as thecircle of confusion. In other words, the light beam will be so small incross section as to represent virtually the light from a single pointfrom the object. This light beam is taken successively from differentpoints of the object until the whole area thereof is covered, and thecoverage must be repeated suiiciently often so that the retentiveness tohuman vision will enable the light from one point to persist until allpoints have been covered.

In motion picture photography it has been found that i6 complete imagesper second give the illusion of continuous motion, and consequently thepresent apparatus may be designed to scan all portions of the surface ofthe object at least 1G times each second. The principle of scanning iswell known as applied to television, but the particular means hereindisclosed is believed to be novel.

The motor ii, having an armature shaft l2 turning at a given speed, isused to drive shafts i5 and i5 at mutually different speeds, asdetermined by the gearing or other motion transmitting connectionsthrough which the shafts i5 and i?,- -re operated from shaft i2. Theexact difference in the rate of rota-tion is not important. It willordinarily be found, however, that the best results will be had when oneshaft rotates almost as fast as the other.

Shafts i5 and i carry mirrors il and i8, respectively, each mirror beingin a plane not quite 90 degrees with reference to the shaft upon whichthe mirror is mounted. lf a beam of light were to strike either -iparallel to the sha-ft upon which the mirror is mounted, the light wouldbe reflected 'upon a conical path and would describe a circle on ascreen at right angles to the shaft axis. The shafts are so xed,however, that the light beams which they reect have angles oi incidenceand reflection which are extremely acute. Thus, the r-e -ected imagewill necessarily comprise an extremely at ellipse, having one elongateddiameter and one diamete' so short as to be negligible. The shafts arefurther oifset angularly with reference to each other about the axis thetransmitted beam so that the elongated diameter of the ellipse producedbyone mirror is approximately at right angles Yto the elongated diameterof the ellipse produced by the other mirror. The resultant effect on abeam of light reflected by both mirrors will give the light sufcientmovement in two different directions to enable it to cover an entirescreen during the continued rotation of the mirrors.

The mirror system is so organized that only one beam of light receivedfrom the object Sl can at any given time be reflected from the mirrorsystem through the orifices lil and 9 of case 8 to reach thephotoelectric cell. The beam received by such orifices is only such ashas been reflected by both mirrors, and the point on the object fromwhich the beam is received is constantly shiftinc in the predeterminedpath, the form and direction of which will depend upon the exactrelative rates of rotation of the two shafts i5 and i6 and the relationof the shafts with respect to the direct path between the object and theorifices ifi and 9.

In general, however, within a wide range of relative R. l?. M. of shaftsE5 and EG, the scanning path will represent what might be called a planeprojection of a deformed or flattened helix moving progressively acrossthe object. The difference in rate of relative rotation of shafts i5 andi6 will represent the pitch of the helix, and it should be so small thatthe pitch or advance of the flattened helical path of the imaginary beamof light described by mirrors i 'i and i8 will represent approximatelythe width of the beam itself so that the beam will cover all portions ofthe surface area during each cycle.

By reason of the described arrangement the photoelectric cell i willreceive light of varying intensity according as the scanning operationproceeds and the beam comes at the moment from a light or other portionof the surface of the object. rEhe photoelectric cell operates in theconventional manner to deliver current acn cording to the intensity ofthe light beam falling thereon, and this current is used to modulate thecarrier wave broadcast by transmitter fi and antenna S.

The modulated carrier wave is received and reproduced in the form of animage by means of the apparatus shown in Figures 2 and 3. A radioreceiver 2i of generally conventional design has an antenna connection Gand a ground connection 5. Therein, apart from the usual amplifyingmechanism, there is a means for employing the amplitude of modulation ofthe carrier wave to vary .the intensity of light given off from aconstant source, such as the lamp 22.

The means by which this is accomplished comprises a pair of overlappingshutters 2li and 25 having small openings 2S which are normallystaggered but may be placed in registry by the amplitude of thevibratory movement of the shutters. To place the shutters in highfrequency vibration at varying amplitudes, I preferably em ploy theso-called piezo-electric crystal effect referred to, for example inPatent No. 1,450,246 and elsewhere. A pair of crystals 2l and 2t aremounted on supports 29, and to them are connected the respectiveshutters 2i?! and 25 in overm lapping relation, as shown in Figure 3.The mounting is preferably remote from the shutters so that the fullexpansion of the crystal is made available for the reciprocation of theshutters. The crystals may be' connected either in parallel or series. Ihave illustrated a series connection by means of a conductor Bil.Conductors 3i and lead to the amplifier or receiver to receive theoutput thereof which is at a frequency which will cause the crystals tovibrate, the amplitude of the vibration being dependent upon theintensity of the inciting signal as received from the transmittingstation.

The light source 22, which is of constant brilliance, is enclosed in a.case 8 like that previously r described, said casing having alignedorifices 9 and if! between which the shutters Eli and 25 are interposed.

When the shutters are overlapped as shown in Figure 5, the apertures 2tthereof will almost be out of registry, but as the crystals expand theoverlap of shutters and 25 will be increased until near or at the fullamplitude the orifices 25 will register with each other and with theorices 9 and if) of the cabinet. Obviously the beam of light passingfrom the source 22 to the aie-'nets orifices Q and it) of thereproducing cabinet will vary in intensity according to the overlap oforifices 26 of the shutters, and since such overlap will depend on theamplitude of crystal vibration, and this in turn upon the intensity ofthe received signal, it will be obvious that I have provided meanswhereby uctuations of current in the photoelectric cell at the sendingstation occasioned by fluctuations of light received by said cellfromthe object, will be enabled to reproduce at the transmitting stationsimilar fluctuations in the intensity of the emitted light.

The light emitted from the source 22 under -the--control'of shutters 2K5and 25 passes the mirror system of a scanning device identical with thatalready described. The motors H at the sending and receiving station arepreferably synchronous motors, operating not only at the same R. l?. butin exact unison so that the cycles of scanning operation of the mirrorsystems in L the two ystations are identical. When this con dition isreached a beam of light from any given point of the object mustnecessarily nd its counterpart in a beam of light from the source 22delivered to exactly the same corresponding point on the screen 35 onwhich the image is reproduced.

As the object is scanned by the mechanism shown in Figure 4, so the saidscreen is scanned in Figures l and 2. For each given point of the objectwhich is thus scanned there is a given intensity of light affecting thephotoelectric cell l, and the effect of such cell produces acorresponding relative intensity of the light beam emitted from thesource 2s, the control of said beam being accomplished by the amplitudeof vibration of the piezo crystals which control the shutters 25- and25. Thus, the image reproduces the object not only in faithful detail asto the point from which the light originates, but also in faithfuldetail as to the intensity of light from each point.

The mirror system herein disclosed provides a means for scanning a largesurface with tremendous rapidity, since there are no reciprocating partsemployed in the scanning device, and no shutters are necessary. Thetransmitting mechanism is receiving one continuous beam of light varyingin intensity according to the point of the object which is its source.The reproducing device is emitting a similar continuous stream of lightgoing to a corresponding point on the screen and havin(T an identicalvariation in intensity. The shutters 2li and at no time wholly interruptthe light from the source .'32 unless there is a total interruption oflight at the object. Thus, the device produces a brilliant illumination.

The use of piezo crystals as a means of controlling the intensity of thelight from source 22 gives a reproducing mechanism which is much moresensitive than it is possible to find in any apparatus which attempts tovary the intensity of the source. No lamp is capable of responding asaccurately or as fast as do the piezo crystals respond in amplitude ofvibration to the intensity of the received signal.

I claim:

l. In television apparatus, a scanning device comprising a pair ofccacting mirrors arranged successively in the path of a beam of light,shafts supporting each of said mirrors and connected with theirrespective mirrors in positions other than normal to the refiectingsurfaces thereof, and means for driving said shafts at different ratesof speed, said shafts being,r oiiset angularly for approximately ninetydeg ees about the axis of the path of said beam of iight.

2. lin television apparatus or the like, the combination with meansdefining the direction of a beam of light, of a succession of mirrors(hsposed in the path of said beam in positions such that said beam isincident upon said mirrors successively at extremely acute angles, meansfor operating said mirrors at diierent rates to vary the angle ofincidence of the beam thereon Within an extremely limited range, andsupports for said mirrors displaced angularly approximately ninetydegrees about the axis of said beam, whereby the varying angle ofincidence and reflection of said beam on successive mirrors will effecta movement of one end of said beam in each of several directionsapproximately at right angles to each other.

3. In a device of the character described, the combination with meansfor dening a given` path for a beam of light at one end of said beam, ofa set of substantially planiform mirrors mounted for rotation about axesdeviating from normal With'reierence to the surfaces of the respectivemirrors and angularly oiset approxi mately ninety degrees about the axisof said beam, said mirrors being arranged in the path of said beam toreect said beam from one mirror to the other successively at slightangles of incidence and reiiection, whereby the beam reflected by eachmirror describes a iiat ellipse, and means for rotating said mirrors atdiffering rates ci speed whereby their composite effect on said beam oi`light involves a scanning movement of said beam in each of twodirections approximately at right angles to each other.

EUGENE CARL MEYER.

